Typically a hydraulic pilot valve consists of a rectangular casing having a pair of side wall ports and a pair of base ports. One of the side wall ports connects the valve to a tank or reservoir of hydraulic fluid, while the other side wall port connects the valve to a source of pressurized hydraulic fluid. The two base ports are work ports which alternately supply pressurized hydraulic fluid to a hydraulic tool.
A pair of lever operated plunger valves control the communication of their respective work ports with either the tank port or the pressurized port. Depressing either of the plunger valves causes its respective work port to communicate with the pressurized port rather than the tank port.
During the operation of the hydraulic tool it is often necessary for the operator to depress a plunger valve via the lever and then remove his hand from the lever in order to operate other controls. In such a situation, it is often desirous to have the lever remain in its activated position rather than spring back to its neutral position.
In the past the lever has been held in position by applying restraints to the handle itself or by utilizing detent devices which engage the activated plunger.
However, handle restraints are cumbersome and awkward to engage and have proven to be unreliable while prior detent devices have been external to the valve itself thus making the control unit larger and changing its basic rectangular shape so as to prevent side-by-side installation of a series of valves.